Refrigerate the pie dough for at least 2 hours before rolling it out. Heat the oven to 375°F with the rack in the lowest position. Crimp or flute the dough in a 9-inch pie dish and partially blind bake it, following the directions for your crust.

Reduce the oven temperature to 350°F. Keep the partially baked crust warm while you make the filling.

Whisk the egg yolks in a medium bowl. In a medium saucepan over medium heat, whisk together the water, filling sugar, cornstarch, filling salt, lemon juice and zest. Cook until the mixture thickens and bubbles, about 6 minutes, then whisk and reduce the heat to low.

Very slowly whisk a few large spoonfuls of the warm lemon mixture into the yolks. Slowly whisk the yolk mixture back into the saucepan. Return to medium heat and cook until thick, with large bubbles bursting at the surface. Remove from the heat and whisk in the butter.

Spread the filling into the warm, partially baked crust. Keep the filling warm while you prepare the meringue.

Beat the egg whites and cream of tartar on medium speed for 1 minute, then on high until soft peaks form, about 4 more minutes. Add the meringue sugar and salt and beat on high until glossy stiff peaks form, about 2 more minutes. Spread over the warm filling all the way to the crust at the edges.

Bake on the lowest rack for 20 to 25 minutes. If the meringue browns too quickly, tent it with foil without letting the foil touch it. Check that the meringue reaches 160°F with a food thermometer. Color alone is not a safety check.

Cool on a wire rack at room temperature for 1 hour, then refrigerate for 4 hours before slicing.